Sulfur-Containing Polymer Matrices for High-Performance Structural CFRPs with Exceptional Thermostability and Metal-like Rigidity

Abstract This work presents a study of high-performance carbon fiber-reinforced plastics (CFRPs) based on sulfur-containing polymer matrices derived from thioglycidyl methacrylate (TGMA) and its reactive oligomers, including compositions chemically modified with elemental sulfur via inverse vulcanization. The synthesized neat matrices demonstrate exceptional dynamic mechanical properties, including a storage modulus (E’) significantly exceeding that of conventional epoxy analogs at both ambient and cryogenic temperatures, with their damping and relaxation behavior being finely tunable by varying the sulfur content. More importantly, CFRPs made with these binders show outstanding adhesion between the matrix and fiber. The result is near-ideal elastic solid behavior, with a peak loss tangent (tanδ) as low as 0.025 and a phase angle δ ≈1.4°, values that point to metal-like rigidity and almost no internal friction under cyclic loading. Unlike conventional epoxy-based composites that suffer a catastrophic drop in stiffness above the glass-transition temperature, the CFRPs developed in this work retain a high storage modulus (up to 37–42 GPa) and, consequently, their structural integrity upon heating beyond 220 °C, which is nearly 100 °C above the matrix Tg, thus demonstrating an extremely low E’ drop of merely ∼5%. This thermal stability, together with tensile strengths approaching 1 GPa and a distinctive brush-like failure pattern that points to efficient energy dissipation and strong fiber–matrix adhesion, makes these sulfur-based materials strong candidates for next-generation structural components suited to aerospace and other high-performance, high-temperature applications that demand the combination of extreme stiffness, thermal stability, and low weight.